1. Field of the Invention
The present invention relates to the papermaking arts, and specifically to the manufacture of bulk tissue and toweling, which may collectively be referred to as bulk tissue. The present invention also relates to the manufacture of nonwoven articles and fabrics by processes such as hydroentanglement. In particular, the present invention relates to belts, which have had a functional polymeric resin material deposited in precise preselected areas onto their base structures to fill those areas and, when desired, to form a layer of desired thickness thereover. Belts of this type are used in the manufacture of bulk tissue and towel, and of nonwoven articles and fabrics.
2. Description of the Prior Art
Soft, absorbent disposable paper products, such as facial tissue, bath tissue and paper toweling, are a pervasive feature of contemporary life in modern industrialized societies. While there are numerous methods for manufacturing such products, in general terms, their manufacture begins with the formation of an embryonic paper web in the forming section of a paper machine. The embryonic paper web is then transferred to a through-air-drying (TAD) fabric or belt by means of an air flow, brought about by vacuum or suction, which deflects the web and forces it to conform, at least in part, to the topography of the TAD fabric or belt. Downstream from the transfer point, the web, carried on the TAD fabric or belt, passes through a through-air dryer, where a flow of heated air, directed against the web and through the TAD fabric or belt, dries the web to a desired degree. Finally, downstream from the through-air dryer, the web may be adhered to the surface of a Yankee dryer and imprinted thereon by the surface of the TAD fabric or belt, for further and complete drying. The fully dried web is then removed from the surface of the Yankee dryer with a doctor blade, which foreshortens or crepes the web and increases its bulk. The foreshortened web is then wound onto rolls for subsequent processing, including packaging into a form suitable for shipment to and purchase by consumers.
As noted above, there are many methods for manufacturing bulk tissue products, and the foregoing description should be understood to be an outline of the general steps shared by some of the methods. For example, the use of a Yankee dryer is not always required, as, in a given situation, foreshortening may not be desired, or other means, such as xe2x80x9cwet crepingxe2x80x9d, may have already been taken to foreshorten the web.
The present application is concerned, at least in part, with the TAD fabrics or belts used on the through-air dryer of a bulk tissue machine. More specifically, the present application is concerned with a TAD belt of the variety developed by Procter and Gamble in the 1980""s and first disclosed in U.S. Pat. Nos. 4,528,239; 4,529,480; and 4,637,859 to Trokhan. The TAD belt in question comprises a foraminous woven element, that is, a woven base fabric, having a coating of a polymeric resin material in preselected areas. The polymeric resin material provides the TAD belt with a macroscopically monoplanar, patterned, continuous network surface which serves to define within the TAD belt a plurality of discrete, isolated deflection conduits or holes. To produce the TAD belt, the foraminous woven element is thoroughly coated with a liquid photosensitive resin to a controlled thickness above its upper surface, and a mask or a negative having opaque and transparent regions which define a desired pattern is brought into contact with the surface of the liquid photosensitive resin and the resin is exposed to actinic radiation through the mask. The radiation, typically in the ultraviolet (UV) portion of the spectrum, cures those portions of the resin exposed through the mask, but does not cure those portions shadowed by the mask. The uncured resin is subsequently removed by washing to leave behind the foraminous woven element with a coating in the desired pattern formed by the cured resin.
The polymeric resin material may alternatively form a plurality of discrete protuberances on its surface by using an appropriately designed mask. That is to say, the plurality of discrete protuberances is the reverse of a continuous network having holes. Instead, the pattern is of discrete areas which are occluded or blocked by the polymeric resin material in an otherwise open foraminous woven element. Belts of this kind may be used in the forming section of a bulk tissue machine to form embryonic paper webs having discrete regions of relatively low basis weight in a continuous background of relatively high basis weight. Belts of this kind may also be used to manufacture nonwoven articles and fabrics, which have discrete regions in which the density of fibers is less than that in adjacent regions, by processes such as hydroentanglement.
Moreover the polymeric resin material may also form a semicontinuous network on the foraminous woven element. That is to say, the polymeric resin material may form, with the use of an appropriately designed mask, a framework of protuberances arranged in a semicontinuous pattern to provide a semicontinuous pattern of deflection conduits. By xe2x80x9csemicontinuousxe2x80x9d is meant that each protuberance extends substantially throughout the belt in an essentially linear fashion, and that each protuberance is spaced apart from adjacent protuberances. As such, the protuberances may be lines which are generally straight, parallel and equally spaced from one another, or may be in the shape of zigzags which are generally parallel and equally spaced from one another.
The present invention is a foraminous woven element, that is, a woven base fabric, for TAD belts of the foregoing types.
The present invention, then, is a base fabric for a through-air-drying (TAD) belt, although it may also be used on the forming, press and dryer sections of a paper machine. As such, it is a papermaker""s fabric which comprises a plurality of warp yarns interwoven with a plurality of weft yarns.
The warp yarns are of two types. Those of the first type weave with the weft yarns in a plain weave, and those of the second type weave with the weft yarns in a 2xc3x972 twill weave. In a plain weave, a warp yarn passes alternatively over and under successive weft yarns, while, in a 2xc3x972 twill weave, a warp yarn passes alternately over and under two successive weft yarns. The warp yarns of the first type alternate with those of the second type, which undulate between adjacent warp yarns of the first type to give the fabric a desired openness.
The present invention will now be described in more complete detail, with frequent reference being made to the figures identified below.